Seasonal changes and migration of longitudinal dunes in the northeastern Rub'al Khali Desert

Abstract

The morphology of small longitudinal dunes responded clearly to wind fields in the northeastern Rub'al Khali Desert. Based on local meteorological data and high-resolution satellite images, we analyzed the wind regime, drift potential (DP), dune morphology changes, and migration rates. The wind roses revealed that two opposing winds (from the northwest and southeast), both at an oblique angle to the dune crest, dominated the structure of the wind regime, with periodic changes between these directions. The annual DP from 2017 to 2019 ranged from 615 to 688 vector units (VU), and the resultant drift potential (RDP) ranged from 149 to 311 VU, indicating a high-energy wind environment. The most erosive winds (DP > 60 VU) occurred from February to June. Controlled by the wind field, dune morphology remained longitudinal from September to May. However, small longitudinal dunes (height below 5 m) transformed into transverse dunes from June to August, and formed a dune network with the large longitudinal dunes. On flat land, a series of active longitudinal dunes migrated at 7.8 to 15.1 m yr−1, with a mean of 11.9 m yr−1. Their dominant migration mode was parallel to the resultant drift direction (RDD), with the dunes extending downwind via accretion at the downwind ends. These dunes also migrate laterally by 0.4 to 0.8 m yr−1 while maintaining a symmetrical longitudinal dune morphology. These results expand our knowledge of dune migration and evolution, and provide guidance for protecting areas such as oases threatened by migrating dunes.